Stack-type thermoresponsive switch having a supplemental heater with annularly-shaped heater portion and terminal regions



Nov. 21, 1967 F. T. PEAQENT ETAL.

STACK-TYPE THERMORESPONSIVE SWITCH HAVING A SUPPLEMENTAL HEATER WITHANNULARLY-SHAPED HEATER PORTION AND TERMINAL REGIONS Filed Aug. 30, 19653 Sheets-Sheet 1 INVENTORS FRANK T /ACE/VT &

BY JOHN m HUFFMAN I Filed Aug. 30, 1965 Nov. 21, 1967 F. T. PIACENT ETAL3,354,278

STACK-TYPE THERMORESPONSIVE SWITCH HAVING A SUPPLEMENTAL HEATER WITHANNULARLY-SHAPED HEATER PORTION AND TERMINAL REGIONS 5 Sheets-Sheet 2TEMPERATURE INVENTORS FAAA/A/ Z P/ACE/VT & BY JOHN W HUFFMAN Maw Nov.21, 1967 F. T. PIACENT ETAL 3,354,278

STACKTYPE THERMORESPONSIVE SWITCH HAVING A SUPPLEMENTAL HEATER WITHANNULARLY-SHAPED HEATER PORTION AND TERMINAL REGIONS Filed Aug. 30, 19653 Sheets-Sheet 5 I -haw L:

VIII!!! INVENTORS FRANK Z /ACEA/7'5( BY JOHN W HUFFMAN United StatesPatent C) 3,354,278 STACK-TYPE THERMORESPONSIVE SWITCH HAVING ASUPPLEMENTAL HEATER WITH ANNULARLY-SHAPED HEATER PORTION AND TERMINALREGIONS Frank T. Piacent and John W. Huffman, Mansfield, Ohio,assignors, by mesne assignments, to Emerson Electric Co., St. Louis,Mo., a corporation of Missouri Filed Aug. 30, 1965, Ser. No. 483,682 12Claims. (Cl. 200122) This invention relates to thermoresponsive orthermostat switch means and more especially to a thermoresponsive switchmeans embodying manual control of the effective temperature operatingrange and incorporating auxiliary or supplemental heating means adaptedto thermally influence the thermoresponsive means.

The invention particularly relates to thermoresponsive switches of theso-called stacked type wherein end regions of switch arms and a bimetalcomponent are insulatingly mounted by circular members to provide acompact construction. Thermostat switches have been used extensively tomaintain automatic control of a predetermined temperature embracedwithin a manual control particularly with appliances embodying heatingelements, such as fiat irons, grills, fry pans and other electricallyenergizable appliances.

In conventional switches of this character, a substantial time lagoccurs in the transfer of heat to the bimetal component resulting in asubstantial temperature differential of the appliance between on and offconditions of the circuit. Supplemental heaters in the form of smallresistance units have been utilized for accelerating the action of thebimetal element, and heretofore supplemental heaters have beenpositioned at regions spaced from the support means or stack assembly ofthe switch components. In such constructions where the resistance heateris spaced from the switch stack or extends outwardly from the stack, theheat responsive means or bimetal element is heated by convection andradiant heat. While such devices accelerate the operation of thethermoresponsive means and promote reduction in temperaturediflerentials of the appliance in circuit with the switch means,appreciable over-run of the temperature is encountered in initialheating of the appliance and the repetitive cycling of the switch meansby the thermoresponsive means or bimetal element is irregular and thetemperature of the controlled appliance is not accurately maintainedwithin a predetermined range.

The invention embraces a thermoresponsive switch mechanism embodyingsupplemental heating means for accelerating and stabilizing the actionof the thermoresponsive means wherein heat from the supplemental heateris transmitted by conduction to the support region of thethermoresponsive means whereby temperature over-run during initialheating of an appliance is eliminated and wherein subsequent repeatedcycling of the switch mechanism under the influence of thethermoresponsive means occurs at constant intervals to accuratelymaintain the appliance within narrow temperature range.

The invention further embraces a switch mechanism of the so-calledstacked type wherein the components of the switch mechanism aresupported by substantially cy- |lindrical mounting means and wherein asupplemental heating means is wholly contained within the support stackwhereby the thermoresponsive means of the switch mechanism is influencedby heat of the supplemental heater conducted through the support stack.

Another object of the invention resides in an auxiliary or supplementalheater for influencing a thermoresponsive means of a stacked switchconstruction wherein the heating element is of generally circularcontour for assembly in the support stack for the switch componentswhere- 3,354,278 Patented Nov. 21, 1967 2 by the heat .developed byelectric energy flow through the heater is eiTe-ctively transmittedthrough the support stack to the thermoresponsive means.

Another object of the invention resides in a circular shaped resistanceheater for incorporation in the support means of a stacked switchwherein the heater is within the confines of the support arrangement toprovide eliective control and transfer of heat by conduction to thebimetal means of the switch mechanism enabling the utilization of theswitch mechanism mounted by the heated body or instrumentality of theappliance or which may be employed as a cycling switch disposed in aposition remote from the heated body or instrumentality of theappliance.

Another object of the invention resides in a novel form of resistanceheater for use in a thermostat switch mechanism wherein portions of theresistance heater are insulated one from another by' circular insulatingmeans whereby the heating unit is embodied in a stacked switch mechanismwithout modification of other components of the switch mechanism.

A further object of the invention is the provision of a supplementalresistance heater which may be incorporated in other types of switchconstruction.

Further objects and advantages are within the scope of this inventionsuch as relate to the arrangement, operation and function of the relatedelements of the structure, to various details of construction and tovcombinations of parts, elements per se, and to economies of manufactureand numerous other features as will be apparent from a consideration ofthe specification and drawing of a form of the invention, which may bepreferred, in which:

FIGURE 1 is an enlarged longitudinal sectional view of a thermostatswitch construction embodying a form of the invention, the switchconstruction being illustrated as mounted on an electrically heatedappliance;

FIGURE 2 is an elevational view of the switch construction shown inFIGURE 1;

FIGURE 3 is a top plan view of the switch construction shown in FIGURE2;

FIGURE 4 is an enlarged top plan view of one form of supplemental heaterelement of the switch construction;

FIGURE 4A is a side view of the construction shown p in FIGURE 4;

FIGURE 5 is an isometric view of an insulating mem her for assembly withthe resistance heater element shown in FIGURE 4;

FIGURE 6 is a plan view of the heater element of FIGURE 4 illustratingthe method of assembly of an in sulating member shown in FIGURE 5;

FIGURE 7 is a view similar to FIGURE 6 illustrating the method ofassembly of the heater element with a second member of the charactershown in FIGURE 5;

FIGURE 8 illustrates a time-temperature graph of a conventionalthermostat switch mechanism embodying a conventional type ofsupplemental heater;

FIGURE 9 illustrates a time-temperature graph of the thermostat switchmechanism embodying the supplemental heater of the invention;

FIGURE 10 is an isometric view illustrating a modified form ofsupplemental heater construction for the thermostat switch andinsulating members in dissembled relation;

FIGURE 11 is an isometric view showing another form of supplementalheater for thermostat switch and insulating members in dissembledrelation;

FIGURE 12 is a fragmentary sectional view showing a method ofcontrolling heat transfer from an appliance to the thermoresponsiveelement of the switch mechanlsm;

FIGURE 13 is a plan view of a control unit embodying a form ofthermostat switch of the invention with certain portions broken away forpurposes of illustration in association with a portion of anelectrically-heated appliance controlled by the unit, and

FIGURE 14 is a longitudinal sectional view through the control unit andthe portion of the appliance illustrated in FIGURE 13.

While the arrangement of the invention is particularly adaptable forcontrolling the temperature of electrically heated appliances, it is tobe understood that the suppiemental heater arrangement may be employedin other forms of control mechanism for influencing a therrnoresponsivemeans.

Referring to the drawings in detail and initially to FIG- URES 1 through3, there is illustrated a form of switch means embodying the inventionas utilized for controlling the temperature of an electrically heatedappliance, such as a flat iron. As shown in FIGURE 1, the electricallyheated iron 10 is inclusive of a base portion or plate 11 embodying aconventional heating means 12 supplied with electric energy from currentsupply lines or conductors L1 and L2 through the switch mechanism. Theiron is provided with a conventional housing 14.

In the arrangement illustrated in FIGURE 1, the base plate llprovides asupport for the switch mechanism, but it is to be understood that theswitch construction may be mountednpon any suitable portion of anelectrically controlled appliance and may be disposed remote from anappliance where the switch mechanism is used as a cycling switch and notunder the direct influence of the heat of an appliance. The switchconstruction illustrated in FIGURE 1 is approximately twice actual sizeand is the type of switch usually referred to as a stacked switch, viz.a switch mechanism wherein the switch components, the bimetal element orthermoresponsive means and circular insulating members are in verticallyspaced stacked relation.

The switch construction is inclusive of a plate or member 16 forming apart of a support means for certain components of the switch, the plate16 being provided with a bore through which extends a sleeve 13.Assembled on the sleeve are switch arms, a thermoresponsive means, asupplemental heater and insulating members. The switch constructionconstitutes a unit, as shown in FIGURE 2, which may be disposed remotefrom an appliance to be controlled. The base plate 11 is provided with athreaded opening to receive the threaded portion 20 of a securing screw22 extending through the sleeve 18 for fixedly mounting the switch uniton the base plate.

The plate 16 is provided with an opening to receive a tenon portion 24of a bushing or fitting 25, the bushing having a flange 26 engaging onesurface of the plate 16, the tenon portion being swaged as at 27 intoengagement with'the lower surface of, the plate 16 fixedly securing thebushing to the plate 16. Disposed within the bushing is a shaft 30having a threaded portion 31 engaging an interiorly threaded region ofthe bushing 25, the shaft being rotatable for manually controlling therelative position of one of the switch arms in a manner hereinafterexplained.

The fitting 25 is provided with an abutment 32 which cooperates with astop means 34 carried by the shaft 30 for limiting the rotative movementof the shaft 39. A manipulating knob 36, shown in broken lines in FIG-URE 1, is telescoped onto the shaft 30, a portion 38 of the stop means34 extending into a groove in the manipulating knob 36 whereby rotationof the knob effects rotation of the shaft 30. The range of rotation ofthe shaft 30 is slightly less than one complete revolution, beinglimited by engagement of the stop means 34 with the abutment 32. Thismovement limiting means for the shaft 30 determines the range oftemperature within which the manual control means may 'be adjusted.

The switch construction is inclusive of a first switch arm or member 40fashioned of a strip of metal adapted to be flexed or moved under theinfluenceof a thermoresponsive means, the switch member 40 beingequipped with a contact 42.

A second flexible switch member 44, formed of a strip of metal, isequipped with a contact 46 arranged for cooperation with the contact 42to complete and interrupt a circuit through the heating element 12in theplate 11 of the iron.

A circular end region of the switch member or arm 40 is provided with anopening to receive a tenon 47 of an annular disc or member 48 ofinsulating material which surrounds the support sleeve 18. A terminalmember St is also provided with an opening to accommodate the tenon 47on the insulating disc 43, the metal terminal 50 being in directmetallic contact with the switch arm 4t} as shown in FIGURE 1. Anannular washer or disc 52 of insulating material on the sleeve 18 isdisposed between the terminal 50 and the support plate 16. The tenon 47insulates both the terminal 50 and the switch member 40 from the supportsleeve 18, the terminal 59 being connected with a current supplyconductor or line L2.

The second switch member 44 has an opening in an end region throughwhich extends an annular insulating member 54. The insulating member 54is provided with a flange 56 and disposed adjacent the flange 56 is asecond terminal or connector 58 connected with the heater 12 in the baseplate 11. Disposed between the switch member 44 and the terminal 58 andmounted on the annular insulating member 54 is a supplementalhe'atingunit 60 for influencing the thermoresponsive means and whichwill be hereinafter described in detail.

The sleeve 18 is provided at its lower end with a flange 62. Mountedbetween the flange and the insulating member 54 is a thermoresponsivemeans or bimetal element 66, the bimetal element having an openingreceiving the sleeve 18. It will be seen from FIGURE 1 that the abovedescribed components comprising the insulating washers or members 52, 48and 54 of circular exterior contour, the switch members 40 and 44, theterminals 50 and 58, and the supplemental heating unit 6% are arrangedin stacked relation on the support sleeve 18. 7

After assembly of these components on the sleeve 18, the upper endregion of the sleeve is swaged as at 68 to secure the support stack ofcomponents in assembled relation. The insulating members or washers 48,52 and 54 are fashioned of lava or insulating ceramic to withstand heatgenerated by the supplemental heating unit 60.

The switch member 44 is adapted to be manually adjusted with respect tothe switch member 40 to a temperature at which it is desired to maintainthe appliance 1i). Disposed between the lower end of the rotatable shaft30 and the switch member 44 is an insulating strut or member 76fashioned of lava or ceramic, one end of the strut being engaged in asocket or recess in the lower end of the shaft 30. The other end regionof the strut 70 is fashioned with a wedge-shaped portion 72 whichengages in a rectangular opening in the switch member 44, thisconstruction preventing relative rotation of the strut ill when.adjusting the shaft 30.

The strut 70 extends through a clearance opening '74 in the switch armd0 as shown in FIGURE 1. Through this arrangement manual rotation of theshaft 30,.through the medium of the strut '70, is effective to adjust orcontrol the relative position of the switch arm 44 to secure the desiredtemperature for the base plate 11 of the appliance 1d. The bimetalelement 66 is flexed by temperature variations for controlling theposition of the switch member 49 to automatically maintain the plate 11or other instrumentality at a predetermined temperature within themanual range of temperature setting or adjustment of the shaft 30. v i

The distal end of the bimetal element 66 is provided with an opening toreceive an insulating member 76, formed of ceramic or lava which issecured to the bimetal element 66 by a'metal clip 78 fashioned with earportions fit which, in assembly, are bent to embrace the edgesof,FIGURES 1 and 2. The

the element 66, as shown in FIGURES 2 and 3. In the arrangement ofswitch mechanism and appliance shown in FIGURE 1, heat from the heatedbase plate 11 influences the bimetal element 66 to cause flexure of theelement upwardly, engaging the lava member 76 with the switch arm 40flexing the switch arm 40 to separate the contacts 42 and 46 andinterrupt the energizing circuit to the base plate 12 when apredetermined temperature of the base plate is attained.

As heat is subsequently dissipated from the plate 11, the temperature ofthe bimetal element 66 is reduced and the element flexed in the oppositedirection, moving the strut 76 away from the switch arm 40 and reengagecontacts 42 and 46. The switch arm 40 is initially tensioned or stressedto bias the switch arm 40 in a direction to normally engage the contacts42 and44 to complete the energizing circuit for the base plate 11.

The present invention embodies a supplemental, auxiliary or acceleratingheater oriented or disposed in the support stack construction of switchcomponents and insulating members shown in FIGURE 1 in a manner wherebyheat from the supplemental heater is conducted through the support stackto the bimetal element 66 where-by the bimetal element is influencedprincipally by conducted heat rather than by convection as insupplemental heating units heretofore utilized to accelerate movement ofa 'bimetal element.

The principle of the supplemental heater of the invention resides infashioning the heating element of a configuration whereby it is whollyWithin the confines of the support stack of the switch components. Forsuch purpose the supplemental heater is preferably of circular shape orcontour. One form of supplemental heater element and associatedinsulating means are'illustrated in FIGURES 4 through 7. The heaterelement is of the resistance type and is fashioned to provide asubstantial length or path of resistance traversed by the current byfashioning the element to provide for traverse of the current in agenerally circular path.

The heating element or resistance unit 86 of the supplemental heater 60is shown per se in FIGURES 4 and 4A. The heating element 86 is fashionedof a fiat sheet of metal and is of generally circular shape and iscomparatively thin as shown in FIGURE 4A. The circular central opening88 of the annularly-shaped or circular heater 86 is of a dimension toslidably fit onto the exterior surface of the annular insulating member54 shown in FIGURE 1. The annular configuration is split or slottedradially as at 90.

A circularly-shaped slot 92 preferably concentric with the circularperiphery of the heating element 86 terminates' at regions 93,configurating the circular element into an annularly-sha-ped outerportion 95 and two semiannularly-shaped inner portions or legs 97 and99, the distal ends of the semiannular portions 97 and 99 beingseparated by a radial slot 100. The unslotted regions 102 and 104 formbridge or connector means integrally connecting the outer annularportion 95 to the inner semiannular portions of legs 97 and 99, asparticularly shown in FIGURE 4.

Regions of the semiannular portions or legs 97 and respectively with theswitch arm 44 and the terminal 58 assembled in the stacked supportformation shown in heater construction is inclusive of twoannularly-shaped insulating members or discs 106 and 106 which are ofidentical construction, member 106 being illustrated in FIGURE 5.

These insulating members are preferably fashioned of heat resistantinsulating material, such as mica, and are made as thin as practicableso as to provide for compact assembly in the support stack construction.

Each of the annular members 106 and 106' is of an exterior diameterpreferably slightly greater than the exterior diameter of the annularportion 95 of the resistance heater 86 to prevent possible currentleakage. The circular opening 110 of each of the annular members 106 and106' is of a diameter to snugly, yet slidably fit onto the annularinsulating member 54, shown in FIGURE 1, each of the members being splitor slotted as at 112 to enable assembly of the insulating members withthe resis'tance heater element 86.

The method of assembling the insulating members 106 and 106' with theheater element 86 is illustrated in FIGURES 6 and 7. With reference toFIGURE 6, the

insulating member 106 is slidably moved laterally in the direction ofthe arrow in assembly with the heater 86 with the terminal leg portion97 and the annular portion at the upper side of the insulating disc 106as viewed in FIGURE 6, with the other terminal leg 99 adjacent theopposite major surface or lower side of the insulating disc 106, anassembly which is made possible through the use of the slot 112.

It should be noted that in assembly the disc 106 is preferably rotatablyadjusted so that the slot 112 is adjacent the terminal region 93 of thecircular slot 92 whereby a terminal portion 114 of the disc 106straddles or covers the slot 90, as shown in FIGURE 6.

The insulating disc 106 is moved in the direction of the arrow inassembly until the exterior periphery of the insulating disc 106 isconcentric with the circular portion 95, in which position the circularcentral opening 88 of the heating element 86 is in registry with thecircular opening in the insulating disc 106.

With disc 106 and heater 86 pre-assembled as above described, thesecomponents are then assembled with the second insulating disc 106'. Inassembling disc 106' with the heater element 86, the insulating disc ismoved in the direction of the arrow, as shown in FIGURE 7, withpreferably adjacent the terminal region 93 of the leg 97 so that aportion 114 of the insulating disc straddles or covers the slot 90 andthe connecting bridges '102 and 104. The disc 106 has been omitted fromFIG- URE 7 for purposes of illustration. As shown in FIG- URE 7, theterminal or leg portion 97 of the inner portion of the heater element 86is above the insulating disc 106'.

Through this method of assembly of the resistance heating element 86with the insulating discs 106 and 106, one terminal leg 99 is exposedand adjacent an outer surface of the insulating disc 106, and the otherterminal leg 97 is at the exposed or outer side of the insulating disc106.

It should be noted that the slots 112 and 112' are at oppositelydisposed regions of the slot 90 in the resistance heater so that theconnecting or bridge sections 102 and 104 are insulated one from theother.

In the final assembly of the pre-assembled heater element and insulatingdiscs 106 and 106 in the switch stack in the manner shown in FIGURE 1,the terminal leg 97 is in direct metallic contact with the switch arm 44and the second terminal leg 99 in direct metallic contact with theterminal 58.

With respect to FIGURES l and 4, the current fiow path through theresistance heater element 86 is as follows: The terminal leg 97 is inengagement with the switch arm 44 and, when the contacts 42 and 46 arein circuit-closing or contacting position, current flows through theterminal leg 97 across the bridge section 102 through the annularportion 95, through slightly less than a complete circle to the bridgesection 104, through the bridge section 104 to the terminal leg 99thence to the terminal 58 which is in metallic contact with the terminalleg 99.

The effective resistance heating length of the element 86 is anelongated path of generally circular shape from the region of engagementof the terminal leg 97 with the switch arm 44 through the bridge 102,the annular portion 95, the bridge 104 and to the region of contact ofthe terminal leg 99 with the terminal or connector 58 of the switchconstruction. Through this method and arrange ment, a substantially longflow path of current through the resistance heater element is providedto produce a. substantial amount of heat in the support stackconstruction shown in FIGURE 1. Substantially all of the heat; isconducted through the stack, viz. through the insulating :member 54 andsleeve 18 to the region of the bimetal. adjacent the flange 56 of theinsulating member and lengthwise through the bimetal element 66.

From the foregoing description it will be apparent that. the heat fromthe circular resistance heater construction or unit 86 is transferred tothe bimetal element 66 substantially entirely by conduction through thestack so that a controlled transfer of heat from the heating unit 36- tothe bimetal element 66 is through the support stack construction. Byvarying the thickness of the flange portion 56 of the insulating member54, the rate of heat transfer by conduction to the bimetal element 66may be accelerated or retarded depending upon the character of controldesired for thermostatically controlling the position of the switch arm40 and hence the automatic cycling of the circuit under the influence ofthe bimetal element 66. Y

The heating unit 86 and insulating discs 166 and 166' provide a compact,adequately insulated supplemental heater wholly embodied in the switchstack or support stack whereby the heat from the heating element forinfluencing the bimetal element is transferred solely through the stack.It is found that through this novel type of supplemental heaterconstruction, more accurate automatic control of the desired temperaturefor an appliance is attained and over-run of temperature during theinitial warm-up of an appliance is eliminated.

FIGURE 8 illustrates a time-temperature curve or graph of a conventionaltype of switch mechanism having a conventional type of supplementalheater disposed outside of the confines of the switch stack and isillustrative of temperature variations during actual cycling operationof such a switch.

During the initial warm-up period of the appliance, the rapid increasein temperature of the appliance is indicated at 120 and, in suchconventional switch without a stack heater of the invention, the initialtemperature of the appliance substantially over-ran the temperaturerange for which the switch is manually adjusted.

The extent of over-run is represented by the line 122, the initialinterruption of the contacts occurring approximately at the point 121 ofmaximum amplitude of the temperature line 120. The line 122 of the graphillustrates the initial period of the circuit, the temperature of theappliance being reduced by normal cooling. Thereafter the on periods orthe circuit closed heating periods of the appliance are illustrated bythe lines 124, and the off periods or periods of circuit interruptionrepresented by the lines 126. From FIGURE 8 it will be seen that therepetitive cycling of a switch embodying a conventional supplementalheater is non-uniform as indicated by the lines 124 and 126 of thegraph.

FIGURE 9 illustrates an actual time-temperature curve or graph of theswitch mechanism of the instant application embodying the circularresistance heater assembled in the support stack and wholly within theconfines of the stack. In the graph of FIGURE 9, the initial Warm-upperiod is indicated by the line 130. It Will be noted from FIGURE 9 thatthere is no initial over-run of tempera ture of the appliance above thetemperature range for which the switch is manually adjusted.

Furthermore the off periods or nonheating periods represented by theline 134 are substantially repetitive in time and the on periods orcircuit energizing periods represented by lines 136 are of substantiallyuniform amplitude whereby the temperature of the appliance is accuratelyheld or maintained within the temperature range for which the switchmechanism is adjusted. It should also be noted from FIGURE 9 that the onand 8 off periods of energization of the appliance occur atsubstantially uniform periods of lapsed time, providing for a more eventemperature of the appliance.

With this arrangement, the circular electrically energizable heater orelement 86 is within the peripheral confines of the annular insulatingmembers of the switch support stack and hence substantially all of theheat generated by current flow through the resistance heater 86 istransferred by conduction through the components in the stack to thesupported area of the bimetal element 66 whereby improved control ofheat transfer to the bimetal element is obtained over priorconstructions.

The construction lends itself to varying the control of transfer of heatto the bimetal element. If a more rapid transfer of heat to the bimetalelement 66 is desired, then the flange 56 of the insulating member 54may be reduced in thickness to change the heat conducting path from theheater to the bimetal element.

The thickness of the circular-shaped mica insulators 166 and 166 may bemodified to vary the rate of heat transfer to the thermoresponsiveelement. If retarded transfer of heat is desired, the thickness of theflange 56 may be increased to thereby increase the length of the heattransfer path through the support stack.

With such arrangement the bimetal element 66, while under the influenceof heat from the base member 11, receives heat by conduction through thesupport stack and by convection from the base member 11. Thesupplemental heat from the heater 86 may be modified as abovementionedto vary the amplitude of temperature differentials between current onand ed periods as well as the frequency of the on and off cyclesdepending upon the characteristics of control desired for the appliance.

The switch mechanism embodying the supplemental heater means, shown inFIGURE 2, may be used for controlling the temperature of an appliancewith the switch mechanism disposed in a position remote from theinfluence of heat from the appliance. For such uses, the switch means isreferred to as a cycling switch. Thus in use of the switch mechanism ata region not under the influence of heat from the appliance, the on andoff periods of energization and de-energization of the appliance throughthe switch mechanism may be varied or modified by changing the rate orrapidity of transfer of heat through the support stack to the bimetalelement 66, the supplemental heater being the only source of heatdirectly influencing the bimetal element.

The effective length of the resistance path of the resistance heaterelement shown in FIGURES 4 through 7 may be varied by changing therelative position of rotation of each of the insulating members 106 and106' with respect to the bridges I02 and 104 between the annular portionand the semicircular terminal leg portions 97 and 95 Thus by furtherrotating the mica insulating disc 106 in a counterclockwise direction,as viewed in FIGURE 6, the effective length of the leg portion 99 incontact with the terminal 58 is shortened.

By rotating the disc 106' a further distance in a clockwise direction asviewed in FIGURE 7, the slot 112 is moved farther away from the slot 99and the length of the leg 97 in contact with the switch member 44 isshortened. By thus shortening the length of contact of the legs 97 and99 with the terminal 58 and switch member 44 respectively, the effectivelength of the resistance path of current flow through the heater isincreased.

Thus the eifective resistance of the heater in developing heat fromcurrent flow therethrough may be varied in a measure by adjusting therelative rotational positions of the insulating discs 166 and 106. Afterassembly of the insulating members, switch components, bimetal element66 and the heater unit 86 on the sleeve 18, the swaging of the sleeve asat 68 compacts the assembly to hold the Q components, including the micainsulating discs 105 and 106, in assembled relatively fixed positions.

FIGURE 10 illustrates a modified form of generally circular resistanceheater for incorporation in the support stack of the switch mechanism.The resistance heater 140 comprises a spirally configurated strip 142providing an annular shape, the inner diameter of the open area definedby the spiral being of a dimension to slidably fit over the insulatingmember 54 shown in FIGURE 1. The strip 142 is comparatively thin and isof a width and thickness to secure the desired resistance factor toprovide supplemental heat in the switch support stack. Insulatingwashers or discs of mica 106a and 106m, which are slotted as at 112a and112aa, provide for assembling the insulating discs with the heater strip142.

The heater strip 142 is preferably provided with two slightly offsetportions 144 and 146 to facilitate assembly and positioning of theinsulating discs 1116a and 166m therewith. The spiral strip 142 hasterminal portions 148 and 150 for contact respectively with the switcharm 44 and the terminal 58 when the heater construction of FIGURE 10 isembodied in the switch construction of FIGURE 1 in lieu of the heaterunit 86. In assembling the disc 106ml with the heater strip 142, theslot 112aa accommodates the offset 144 whereby the terminal portion 148of the heater strip 142 is above the insulating disc 106aa.

In assembling the insulating disc 106a with the heater strip 142, theslot 112a accommodates the offset 146 whereby the terminal portion 150is beneath the insulating disc 106a. The effective resistance heatingarea or length of the heater strip 142 is the circular distance betweenthe offset regions 144 and 146 which distance is schematically indicatedby the circular line 152, this portion being insulated by the insulatingdiscs from the terminal portions 148 and 150.

It is to be understood that the effective length of the resistanceportion of the strip indicated by the line 152 may be lengthened orshortened by changing the relative positions of the offset portions144.and 146 so long as the resistance path is less than a completecircle and the offset regions 144 and 146 maintained out of alignment orregistration. The inner diameter of each of the insulating discs 106aand 106ml is of a dimension to snugly fit over the insulating member 54shown in FIGURE 1. Thus the heater construction shown in FIGURE 10 in astacked switch construction supplies supplemental heat for influencing abimetal element such as bimetal element 66 of FIGURE 1.

FIGURE 11 illustrates another modification of resistance heater of acircular type for assembly within the confines of a switch supportstack. The heater construction 1d0, shown in FIGURE 11, comprises aresistance element 162 which may be resistance wire of circular crosssection, shaped to a spiral configuration with the circular areaencompassed by the spiral of a dimension to snugly fit on the insulatingmember 54 shown in FIGURE 1.

The configuration of heater 160 is similar to that shown in FIGURE 10,the wire having offset regions 164 and 166 providing terminal portions168 and 170 for contact respectively with the switch arm 44 and theterminal 58 when embodied in the switch construction shown in FIG- URE 1as a supplemental support stack heater.

In this form, annularly-shaped mica insulating discs or members 106 band 1106b]; are assembled with the resistance wire 162 in a mannersimilar to that shown in FIGURE 10. In assembling the insulating disc106bb with the resistance wire 162, the slot 112bb accommodates theoffset 164 with the terminal portion 168 above the insulating disc106bb. In assembling the insulating disc 1116b with the resistanceheater, the slot 112 b accommodates the offset 166 and the terminalportion 170 is beneath the insulating disc 1116b.

The effective spiral resistance path is that portion of the resistancewire 162 between the offset regions 164 and 16 166, this circular pathbeing indicated schematically by the circular line 172. The heater andinsulating disc components shown in FIGURE 11, assembled as abovedescribed, may be embodied in the switch stack of the character shown inFIGURE 1 to provide supplemental stackconducted heat for influencing thebimetal element.

The effective resistance heating length of the Wire 1162, viz the lengthof the path indicated by the circular line 172 may be lengthened orshortened by changing the positions of the offset regions 164 and 166 solong as the circular path 172 is less than a complete circle and theoffset regions 164 and 166 maintained out of alignment or registration.

FIGURE 12 is a fragmentary sectional view similar to a portion of theconstruction shown in FIGURE 1 illustrating a means of controlling orretarding heat transfer from a heated appliance to the bimetal elementin order to vary the heat transferred from the appliance to the bimetalelement. As shown in FIGURE 12, the appliance includes a base plate 11'to which is attached the stacked switch mechanism by means of a member22 extending through the support sleeve 18 of the switch support stack.The switch includes a first switch arm 40' and a second switch arm 44having cooperating contacts 42' and 46 and a thermoresponsive means orbimetal element 66' arranged to influence the position of the switch arm40 through an insulating strut 76.

These components are mounted in a stack in the same manner as shown inFIGURE 1, the stack including a supplemental heater unit 6! or one ofthe heater constructions shown in FIGURE 10 or FIGURE 11.

Disposed between the flange 62 of the metal sleeve 18' and the bimetalelement 66' is an insulating member 176 which may be mica, lava, ceramicor other suitable heat resistant insulation material. The insulatingmember 176 retards heat transfer from the appliance member 11' to thebimetal element 66' enabling a degree of control of the cycling of theswitch even though the bimetal element 66' is also responsive to heatfrom the appliance 11'.

FIGURES l3 and 14 illustrate a removable unit control for a cookingappliance, such as a skillet or fry pan 180 equipped with anelectrically energizable heating unit 182 provided with male terminals184 for connection with a removable heater control unit 186 for theskillet or other appliance. The skillet or cooking appliance 181 isequipped with a cylindrically-shaped heat transfer projection or heatconducting portion 188 preferably disposed midway between the maleterminals 184 as shown in FIGURE 13, the projection 188 being adapted toconduct heat from the skillet or appliance 180 to the control unit 186.

The terminals 184 are insulated from the metal utensil by insulatingmembers 193. The circuit controlling unit 186 is arranged to be readilyconnectable with and removable from the appliance 180.

The switch mechanism is of the stacked switch type including a circularstack heater construction of the in vention and is enclosed within asuitable housing 192 fashioned of rigid molded insulating material suchas Bakelite having a base portion 194 and a cover portion 195. The baseportion and cover portion mate at a juncture line 196 and are heldtogether by screws 197.

The base and cover sections of the housing are shaped to providerecesses 198 accommodating female-type connector clips 2% which engagethe terminals 184 when the control unit 186 is in operative connectionwith the appliance Enclosed within the housing 192 is a stacked switchmechanism of the character illustrated generally in FIGURE 1 andincludes a support plate 160, a first switch arm 400, a second switcharm 440, a bimetal element or thermoresponsive means 116a and asupplemental heater 86c which are assembled on a member 18c which, inthe arrangement shown in FIGURE 14, may be either of solid cross sectionor of the tubular shape.

appliance 180. threaded openings accommodating a threaded The switchmembers are respectively provided with contacts 42c and the forcontrolling a circuit through the The support plate lbc is provided withshaft 2&2 equipped with a manipulating knob 2%. A rigid strut "i i-c isdisposed between the threaded shaft 202 and the switch member 440 formanually adjusting the relative position of the switch member 440 forthe temperature range desired for the appliance.

The support stack arrangement of the switch construction includes a heatconducting or heat transfer member or bar 268 having a fiat portion 2163which is assembled in the stack support construction and is preferablyin direct contact with the bimetal element 660 for transferring heat tothe bimetal element. Also assembled in the stack switch construction isa plate or contact member 2110 which is intercalated in the circuit andis engaged by lower terminal portion of .the supplemental heater 860,the upper terminal portion of the heater directly engaging the switcharm Me in the same manner as illustrated in FIGURE 1.

As shown in FIGURE 14, the current conducting member 210 is connccted inthe switch circuit and is engaged by a lower terminal of thesupplemental heater construction 86c. Annular insulating members mountedon the member 180 insulate the switch members and the member 210 fromthe member 180. A supplemental heater 860 is in circuit with the switcharm his in the same manner as illustrated in FIGURE 1 and is energizedwhen the contacts 420 and dds are engaged to establish current flowthrough the supplemental heater 36c and through the appliance when theclips Ztlii are engaged with the terminals 184.

The heat transfer member or bar 2&8 is fashioned with I a comparativelyshallow recess 212 which receives the heat transferprojection 188 whenthe connectors or terminals Ztltl and 184 are in fully engaged relation.

The heat from the appliance heating unit 132 is transferred by theprojection 18% and the bar 2% to the bimetal element 66:: forinfluencing the relative position thereof to automatically control theappliance within the heat range for which the manually actuable switcharm 440 has beenadjusted.

The supplemental heater ssc supplies additional heat conducted throughthe support stack to the bimetal element 65c in the manner hereinbeforedescribed in reference to the switch mechanism shown in FIGURE 1 forpreventing initial over-run of the temperature of the appliance and toobtain repetitive cycling action through making and breaking the circuitthrough the contacts 420 and 460 to obtain a temperature control of theappliance of the character illustrated schematically in FIGURE 9.

The control unit receives current through conductors L1 and L2 connectedwith a conventional current supply. The control unit 186 is providedwith a transparent Window 214 anda pilot light (not shown) disposedbeneath the window 214 for indicating to a user when an energizingcircuit is completed through a switch mechanism to the appliance, thelight being intercalated in the circuit in a conventional manner so thatit is de-energized when the circuit is interrupted by separation of thecontacts 420 and 460.

Thus, the supplemental heater 860 provides heat for accelerating theaction or movement of the bimetal element are to control the temperatureof the appliance. It is to be understood that the heater constructionsshown in FIGURES l and 11 may be embodied in the switch constructionshown in FIGURES l3 and 14 in lieu of the supplemental heaterconstruction 86c. The arrangement in FIGURES 13 and 14, embodying thecircular supplemental heater construction, provides for transfer of heatthrough the support stack of the switch arrangement to the bimetalelement by conduction and thereby effecting a more accurate control ofthe heating of the 7 l2 appliance as exemplified in the graphicrepresentation of FIGURE 9.

It is apparent that, within the scope of the invention, modificationsand different arrangements may be made other than as herein disclosed,and the present disclosure is illustrative merely, the inventioncomprehending all variations thereof.

We claim:

ll. Switch mechanism, in combination, switch. means including arelatively movable switch arm, a pair of cooperating switch contacts,one of said contacts being carried by the switch arm, a bimetal member,support means for said switch arm and bimetal member includinginsulating means retaining said arm and bimetal member in spacedrelation, said bimetal member being disposed to inliuence the relative.position of the other of said contacts, an electrically-energizableheating element mounted by said insulating means having anannularlyshaped heating portion and terminal portions for connection incircuit with said contacts, disc means of insulating material embracingboth sides of the heating portion of said heating element intermediatethe terminal portions, said heating element and disc means being mountedby the insulating means whereby heat generated by current flow throughthe heater is conducted to the bimetal member through the insulatingmeans.

2. Switch mechanism, in combination, switch means including a relativelymovable switch arm, a pair of cooperating switch contacts, one of saidcontacts being carried by the switch arm, a bimetal member, insulatingmeans retaining said arm and bimetal member in spaced relation providinga support stack, said bimetal member being disposed to influence therelative position of the other of said contacts, anelectrically-energizable resistance heating element mounted by saidinsulating means having an annularly-shaped heating portion and terminalportions for connection in circuit with said contacts, disc means ofinsulating material embracing both sides of the heating portion of saidheating element intermediate the terminal portions, said heating elementand disc means being mounted in the support stack whereby heat generatedby current flow through the heater is conducted through the stack to thebimetal member.

3. Switch mechanism, in combination, switch means including relativelymovable current conducting switch arms, a'bimetal thcrmoresponsivemember, an end region of each of said switch arms and bimetal memberbeing supported by circular members of insulating material providing asupport stack, an electrically energizable heating means including acircularlyehaped resistance element having an annularly-shaped heatinportion and terminal regions in circuit with said switch means, a pairof discs of insulating material respectively embracing both sides of theheating portion of said circularly-shaped heating element, said heatingelement and the discs of insulating material being disposed in thesupport stack whereby heat from the resistance element is conducted tothe bimetal member through the stack to control the relative position ofone of said switch arms, and manually actuable means for controlling therelative position of the other of the switch arms.

4. Switch mechanism including, in combination, a support member,insulating means including annular members of insulating materialdisposed in stacked relation on the support member, switch arms mountedin spaced relation by the insulating means, said switch arms havingcooperating contacts, a bimetal element mounted on said support means,strut means between said bimetal element and one of said switch armsadapted to engage and influence the relative position thereof uponfiexure of said bimetal element, a resistance heating element mounted bythe insulating means having an annularly-shaped heating portion andterminal regions for connection in circuit with said contacts, discmeans of insulating material em- 13 bracing both sides of the heatingportion of said heating element intermediate the terminal portions, saidannularly-shaped heating portion being disposed within the peripheralconfines of the disc means whereby heat generated by current flowthrough the heating element is conducted through the support means tothe bimetal element.

5. Switch mechanism including, in combination, support means, a pair offlexible switch arms insulatingly mounted by the support means andhaving cooperating contacts, a bimetal element mounted by the supportmeans and having insulating means arranged to engage one of said switcharms for influencing the relative position thereof, a resistance heatingelement insulatingly mounted by said support means, said heating elementhaving an annularly-shaped heating portion and terminal portionsconnected in circuit with one of said switch arms whereby current flowthrough the heating element is controlled by engagement anddisengagement of the contacts, annularly shaped insulating discsembracing both sides of the heating portion intermediate the terminalportions, the annul'arly-shaped heating portion of the heating elementbeing disposed within the peripheral confines of said insulating discswhereby heat generated by current flow through the heating element istransmitted by conduction through the support means to the bimetalelement.

6. Switch mechanism, in combination, switch means including a flexibleswitch arm, a pair of cooperating switch contacts, one of said contactsbeing carried by the switch arm, a bimetal element, support means forsaid switch arms and bimetal element including circular members ofinsulating material arranged in a stack, said bimetal element beingdisposed to influence the relative position of the other of saidcontacts, an electrically energizable heating element having anannularly-shaped resistance heating portion and curved terminal legportions integrally connected with the resistance heating portion, theterminal leg portions being in annulated relationship with the heatingportion, a pair of annular discs of insulating material, each dischaving a radial slot, said discs being disposed respectively at oppositesides of the annularly-shaped resistance heating portion with the slotsaccommodating the terminal leg portions for insulating theannularly-shaped resistance heating portion from the terminal legportions.

7. Switch mechanism, in combination, switch means including a flexibleswitch arm, a pair of cooperating switch contacts, one of said contactsbeing carried by the switch arm, a bimetal element, support means forsaid switch arms and bimetal element including circular members ofinsulating material arranged in a stack, said bimetal element beingdisposed to influence the relative position of the other of saidcontacts, electrically energizable heating means including acircularly-shaped heating element having an annularly-shaped resistanceheating portion and annularly-shaped terminal leg portions integrallyconnected with the resistance heating portion and in annulated relationtherewith, a pair of annular discs of insulating material, saidcircularly shaped heating element and said discs being mounted on andsurrounding the support means, each disc having a radial slotaccommodating a terminal leg portion, one of said discs being disposedbetween one major surface of the annularlyshaped heating portion and oneterminal leg portion and the other of said discs being disposed betweenthe other major surface of the heating portion and the other terminalleg portion for spacing the annularly-shaped heating portion from theterminal leg portions.

-8. Switch mechanism, in combination, switch means including a flexibleswitch arm, a pair of cooperating switch contacts, one of said contactsbeing carried by the switch arm, a bimetal element, support means forsaid switch arm and bimetal element including circular members ofinsulating material arranged in a stack, said himetal element beingdisposed to influence the relative position of the other of saidcontacts, electrically energizable heating means including anannularly-shaped heating portion and curved terminal portions disposedin said stack, a pair of insulating discs disposed respectively atopposite sides of said heating portion for spacing the heating portionfrom the terminal portions, said heating portion and terminal portionsbeing within the confines of said insulating discs and in circuit withsaid contacts whereby current flow through said heating element whensaid contacts are in closed position establishes heat conducted throughthe stack to said bimetal element for actuating the bimetal element.

9. Switch mechanism, in combination, switch means including a flexibleswitch arm, a pair of cooperating switch contacts, one of said contactsbeing carried by the switch arm, a bimetal element, support means forsaid switch arm and bimetal element including circular members ofinsulating material arranged in a stack, said bimetal element beingdisposed to influence the relative position of the other of saidcontacts, electrically energizable heating means including acircularly-shaped element in said stack, said heating element having acircular slot and a radial slot forming an annular resistance heatingportion and two terminal portions, said terminal portions being inannulated relation with the annular heating portion and integrallyjoined with the annular heating portion by connecting bridge portionsdefined by the radial slot whereby current flows from one terminalportion through the annular portion to the other terminal portion, apair of insulating discs adjacent said heating element, one of saiddiscs being disposed between one major surface of the annular heatingportion and a terminal portion and the other of said discs beingdisposed between the other major surface of the heating portion and theother terminal portion for spacing the annular heating portion from theterminal portions, said heating element being within the confines ofsaid insulating discs and in circuit with said contacts whereby currentflow through said heating element when said contacts are in closedposition establishes heat conducted through the stack to said bimetalelement for actuating the bimetal element.

10. An accelerating heater for a stacked switch construction embodying athermoresponsive means influenced by the heater comprising acircularly-shaped heating element having an annular resistance heatingportion and annularly-shaped terminal leg portions integrally connectedwith the resitsance heating portion and in annulated relation therewith,a pair of annular discs of insulating material, each disc having aradial slot accommodating a terminal portion, one of said discs beingdisposed between one major surface of the annular heating portion and aterminal portion and the other of said discs being disposed between theother major surface of the heating portion and the other terminalportion for spacing the annular resistance heating portion from theterminal leg portions whereby current flows through the resistanceheating portion in a circular path from one terminal leg to the other.

11. An accelerating heater for a stacked switch construction embodying athermoresponsive means influenced by the heater comprising acircularly-shaped heating element having an annularly-shaped resistanceheating portion and curved terminal leg portions integrally connectedwith the resistance heating portion and interiorly annulated within theheating portion, a pair of annular discs of insulating material, eachdisc having a radial slot accommodating a terminal leg portion, one ofsaid discs being disposed between one major surface of the heatingportion and a terminal portion and the other of said discs beingdisposed between the other major surface of the heating portion and theother terminal portion for spacing the annularly-shaped resistanceheating portion from the terminal leg portions whereby current flows ina circular path through the resistance heating portion.

12. An accelerating heater for a stacked switch construction embodying athermoresponsive means influenced by theheater comprising anelectricallyenergizable circularly-shaped heating element having acircular slot and a radial slot forming an annular resistance heatingportion and annularly-shaped terminal portion in annulated relation withthe heating portion, said terminal portions being integrally joined withthe annular portion by connecting bridge portions defined by the radialslot whereby current flows from one terminal portion through the annularportion to the other terminal portion, a pair of insulating discsadjacent said heating element, one of said discs being disposed betweenone major surface of the annular heating portion and aiterminal portionand the other of said discs being disposed between the other major 16surface of the heating portion and the other terminal portion forspacing the annular portion from the terminal portions, said heatingelement being within the confines of said insulating discs.

References Cited UNITED STATES PATENTS 8/1958 Huffman 200-122 X 6/1965Levinn 200-122

1. SWITCH MECHANISM, IN COMBINATION, SWITCH MEANS INCLUDING A RELATIVELYMOVABLE SWITCH ARM, A PAIR OF COOPERATING SWITCH CONTACTS, ONE OF SAIDCONTACTS BEING CARRIED BY THE SWITCH ARM, A BIMETAL MEMBER, SUPPORTMEANS FOR SAID SWITCH ARM AND BIMETAL MEMBER INCLUDING INSULATING MEANSRETAINING SAID ARM AND BIMETAL MEMBER IN SPACED RELATION, SAID BIMETALMEMBER BEING DISPOSED TO INFLUENCE THE RELATIVE POSITION OF THE OTHER OFSAID CONTACTS, AN ELECTRICALLY-ENERGIZABLE HEATING ELEMENT MOUNTED BYSAID INSULATING MEANS HAVING AN ANNULARLY SHAPED HEATING PORTION ANDTERMINAL PORTIONS FOR CONNECTION IN CIRCUIT WITH SAID CONTACTS, DISCMEANS OF INSULATING MATERIAL EMBRACING BOTH SIDES OF THE HEATING PORTIONOF SAID HEATING ELEMENT INTERMEDIATE THE TERMINAL PORTIONS, SAID HEATINGELEMENT AND DISC MEANS BEING MOUNTED BY THE INSULATING MEANS, WHEREBYHEAT GENERATED BY CURRENT FLOW THROUGH THE HEATER IS CONDUCTED TO THEBIMETAL MEMBER THROUGH THE INSULATING MEANS.